Conventional Liquid Crystal Device (LCD) displays form images by modulating the polarization state of illumination that is incident to the display surface. In a typical back-lit LCD display, an arrangement of polarizers is used to support the LCD modulation, including a rear polarizer, between the LCD and the light source, to provide polarized light to the LCD spatial light modulator and a front polarizer, acting as an analyzer. (By definition, the front polarizer is designated as the polarizer closest to the viewer.) In operation, each pixel on the display can have either a light state, in which modulated light that is aligned with the transmission axis of the front polarizer is emitted from the display, or a dark state, in which light is not aligned with the transmission axis of the front polarizer and is effectively blocked from emission.
Referring to FIG. 11, there is shown, in summary form, the behavior of key components of a liquid crystal display for handling incident polarized light to each pixel, showing the symbols and graphic conventions used in subsequent description. Orthogonal P- and S-polarization states are indicated by lines or circles, respectively, superimposed on arrows that indicate incident light direction. Transmission axes are similarly indicated by a double-sided arrow or a circle. An absorptive polarizer 50a, 50b, transmits polarized light that is aligned with its polarization axis and absorbs polarized light that is orthogonally oriented. By comparison, a reflective polarizer 52a, 52b transmits polarized light that is aligned with its polarization axis and reflects polarized light that is orthogonally oriented. An individual LC component 54a/54b modulates the incident beam by modulating the substantially polarized illumination beam in pixel-wise fashion. Following the convention used in this specification, an off state LC component 54a rotates the polarization of incident light. An on state LC component 54b does not rotate the polarization of incident light. The general nomenclature “LC component”, as used in this disclosure, applies to a light-modulating element on the LCD spatial light modulator itself. The LCD spatial light modulator can be considered as an array of LC components 54a/54b. 
There are two possible states for any pixel modulated by the LCD spatial light modulator: a dark state and a light state. In this application, the terms “dark state” and “light state” are used to describe the pixel state; the terms “on state” and “off state”, as noted above, refer to the polarization activity of the LC component itself, rather than to the pixel state that is represented.
It is significant to observe that the characteristics of each type of LCD spatial light modulator determine whether or not the on state of each LC component provides a dark state or light state to its corresponding pixel. As stated above, the examples illustrated in the present application use the following convention:
(i) an on state LC component 54b provides a dark state pixel;
(ii) an off state LC component 54a provides a light state pixel. However, the opposite pairing of on and off states to light and dark state pixels is also possible. For subsequent description in this application, except where specifically noted otherwise, the convention stated here and illustrated in FIG. 11 applies.
In addition to supporting components for polarization and polarized light recycling, an LC component also has a Color Filter Array (CFA) in typical applications. FIG. 1 shows a conventional arrangement of LCD display 10 with a front polarizer 50a, rear polarizer 50b, a backlight unit 56, a reflective film 57, with off state LC component 54a that converts S-polarization (circle) to P-polarization (line) and, conversely, converts P-polarization to S-polarization. An on state LC component 54b performs no polarization conversion. Both off state LC component 54a and on state LC component 54b are shown segmented into three separate sections for the three color components of each pixel. A color filter array 60, in the path of the modulated beam formed by the array of LC components 54a and on state LC components 54b, provides a corresponding arrangement of color filters, labeled 60r for red, 60g for green, and 60b for blue. (For simplicity, individual color filters 60r, 60g, and 60b are labeled only when necessary in subsequent figures.) In conventional LC component designs, component color filters 60r, 60g, and 60b of color filter array 60 are absorptive.
As is well known, display images are typically formed using multiple colors in combination (red+green+blue, for example) in the modulated beam. To allow more straightforward description, FIGS. 1-10D are simplified to show the handling of light of only a single color (typically one of red, green, or blue light) at a time. In practice, multiple colors would be handled as described for the embodiments of FIGS. 1-10D.
Unpolarized light is emitted from backlight 56. In this light state, only light having S-polarization is transmitted through rear polarizer 50b. The intended light for each red (R), green (G), or blue (B) color component is transmitted through its corresponding component color filter 60r, 60g, or 60b of color filter array 60; other colors are absorbed by the other two component color filters 60r, 60g, or 60b. Only P-polarized light transmitted through off state LC component 54a is transmitted through front polarizer 50a; S-polarized light is absorbed by front polarizer 50a. 
Due to absorption by rear polarizer 50b and absorption by color filter array 60, only about ⅙ of the available light can be provided at the output for a single light pixel. It can be readily appreciated that there would be benefits to component arrangements that increase the amount of available light for each light pixel.
Referring to FIG. 2, there is shown the arrangement of a conventional LC display 10 that increases the available light by polarization recycling. Here, a reflective polarizer 52b is disposed between backlight unit 56 rear polarizer 50b. This arrangement provides an approximately 2× increase in available brightness over the conventional arrangement of FIG. 1.
Additional brightness increase can be obtained using color recycling, with a reflective color filter array 62b, as is shown in the example of FIG. 3A. Using reflective color filter array 62b, the absorption requirement for color filter array 60 is greatly reduced and more light is provided, yielding up to about a 3× brightness increase over the conventional arrangement of FIG. 1. FIG. 3B shows an alternate arrangement using reflective color filter array 62b between rear polarizer 50b and the LC component. Since rear polarizer 50b is absorptive and is in the path of light recycling by the reflective color filter array 62b, the FIG. 3B arrangement yields, for a light pixel, about half of the brightness of the arrangement of FIG. 3A. Polarization and color recycling can be provided by a single film component, as is described in the article entitled “Cholesteric Colour Filters for Reflective and Transmissive LCDs” by R. T. Wegh, C. Doornkamp, and J. Lub in pp. 305-308 of Eurodisplay 2002. Referring to FIG. 4A, there is shown a schematic of a conventional LC display 10 arrangement using a reflective polarizing color filter array (RPCFA) 63b, as described in the Wegh et al. article. FIGS. 4B and 4C show two different arrangements of RPCFA 63b. In FIG. 4B, RPCFA 63b has its component reflective color filter array 62b atop its reflective polarizer 52b with respect to backlight unit 56. In FIG. 4C, the reverse arrangement is used, with reflective polarizer 52b atop reflective color filter array 62b relative to backlight unit 56. This component can also include a quarter-wave plate.
As can be appreciated from the above description, reflective polarizers and reflective color filter arrays can help to increase light output of an LC display device. In conventional practice, a number of rules-of-thumb apply for placement of these film components in the layered arrangement of the LC display 10, as was shown in FIGS. 2, 3A, 3B, 4B, and 4C:
(i) Reflective polarizer 52b is positioned between backlight unit 56 and rear polarizer 50b. Otherwise, rear polarizer 50b must absorb half of the incident light, that is, light having a polarization state orthogonal to its transmission axis.
(ii) Reflective color filter array 62b is placed between backlight unit 56 and LC component 54a/54b. In addition, conventional practices would direct placement of reflective polarizing color filter array (RPCFA) 63b to some position between backlight unit 56 and LC component 54a/54b. 
The conventional arrangement using a reflective polarizer, as summarized in FIGS. 2A-2D, is described in a number of patent disclosures, including:
U.S. Pat. No. 6,661,482 entitled “Polarizing Element, Optical Element, and Liquid Crystal Display” to Hara;
U.S. Pat. No. 5,828,488 entitled “Reflective Polarizer Display” to Ouderkirk et al.;
U.S. Patent Application Publication 2003/0164914 entitled “Brightness Enhancing Reflective Polarizer” by Weber et al.; and,
U.S. Patent Application Publication 2004/0061812 entitled “Liquid Crystal Display Device and Electronic Apparatus” by Maeda.
It is known to use different types of polarizers with an LC display in order to achieve specific effects, depending on how the display is used. For example, U.S. Pat. No. 6,642,977 entitled “Liquid Crystal Displays with Repositionable Front Polarizers” to Kotchick et al. discloses a liquid crystal display module for a portable device, wherein the front polarizer may be any of a number of types and can be tilted or positioned suitably for display visibility. Similarly, U.S. Patent Application Publication Ser. No. 2003/0016316 entitled “Interchangeable Polarizers for Electronic Devices Having a Liquid Crystal Display” by Sahouani et al. discloses a device arrangement in which different types of front polarizers may be removably interchanged in order to achieve a suitable display effect. Among possible arrangements noted in both the '977 Kotchick et al. and the '16316 Sahouani et al. disclosures is the use of a reflective polarizer as the front polarizer for an LC display. It is significant to note that both the '977 Kotchick et al. and the '16316 Sahouani et al. disclosures emphasize that this arrangement would not be desirable in most cases, except where special “metallic” appearance effects, not related to increased brightness and efficiency, are deliberately intended. As both the '977 Kotchick et al. and the '16316 Sahouani et al. disclosures show, established practice teaches the use of reflective polarizer 52b between the illumination source, backlight unit 56, and rear polarizer 50b, as is shown in the arrangement of FIG. 2, for improved brightness and efficiency. Established practice clearly does not use reflective polarizer 52b on the viewing side of LC component 54a/54b, except, where a “metallic-looking” display appearance is desired, as a less desirable substitute for front polarizer 50a. The use of a reflective polarizer in the place of front polarizer 50a causes a dramatic loss in contrast ratio, effectively eliminating any possible benefit in increased brightness.
While conventional placement of reflective polarizers, reflective color filter arrays, and RPCFAs provides a measure of increased efficiency and brightness for LC displays, there is a recognized need for improvement in display brightness, without adding cost or complexity to existing designs.